Estudo das Propriedades Estruturais e Vibracionais do Titanato de Cobalto dopado com Ni e Mg.

Abstract

In this work there is an interesting in understanding how nickel (Ni2+) and magnesium (Mg2+) interact in the compound AxCo1-xTiO3, in its structural and vibrational properties, after atomic substitution in cobalt titanate (CoTiO3). The synthesis was performed bythe solid-state reaction method, at regular intermissions of 0.1 at concentrations 0.0 ≤ x ≥ 1.0, being A = Ni2+ or Mg2+. Cobalt, Nickel (NiTiO3) and Magnesium (MgTiO3) titanates have an ABO3 ilmenite structure, in which the alternates cause a change in the characteristics and properties of the samples, in case of any substitution through the A and/or B cátions, capacitors, pigments, lubricants, gas sensors, photovoltaic cells, among others. To characterize these structures, two experimental techniques were used, X-ray diffraction (XRD) and Raman spectroscopy. It hs been observed that, for the reference samples, the X-ray diffraction patterns and the Raman spectra are in agreement with the results found in the literature. Nonetheless, in MgTiO3 we have a small fraction of the MgTi2O5 phase. The cationic replacement of Co2+ by Ni2+, in the compound NixCo1-xTiO3, showed small changes in the diffractograms, appearing some peaks of low intensity. In the Raman spectroscopy measurements of the same system, it was possible to see that the substitution provides a subtle change in the positions of some vibrational modes. On the other hand, in the MgxCo1-xTiO3 system, changes in diffraction peaks wereobserved at some concentrations. In the Raman spectra of MgxCo1-xTiO3, we observed that at concentrations 0.7 to 0.9 there were greater changes in the spectrum, exhibiting the effect of emergence and displacements of new peaks. Regarding the width of the peaks, a structural disorder was observed only in the system with Mg2+. For Raman spectroscopy measurements with temperature different from the environment, the structure of NixCo1-xTiO3 underwent a shift in the central position of each peak to lower wavenumbers and a widening in vibrational modes with temperature variation. The atomic substitution in the NixCo1-xTiO3 and MgxCo1-xTiO3 systems proved to be fascinating, presenting the formation of a solid solution. In addition, the behavior of the unit cell of these compounds was also investigated, knowing that the ionic rays of Ni2+ and Mg2+ are closer to the number of the radius of Co2+ and that the value of the atomic mass of Ni2+ is closer to the value of the mass of Co2+. In spite of that, for Mg2+the atomic mass is less than half the mass value of Co2+. The results indicated an increase of the unit cell in one system and the reduction of the unit cell in another system. We hope that, with the research undertaken, the compounds produced, NixCo1-xTiO3 and MgxCo1-xTiO3, will contribute to new technological applications resulting in materials with great importance and that their characteristics, both synthese, structural and vibrational will help to elucidate various types of physical and chemical systems.